Buried injection logic (BIL) circuits are a type of logic circuits which can be implemented on bipolar analog integrated circuits. The characteristics include low voltage, low power, medium speed, and compact size. These circuits permit mixing of analog and digital functions on a single chip. Because these circuits have low power and low voltage, however, they cannot drive external circuits directly but require some type of buffer.
Furthermore, use of conventional digital type gates on analog integrated circuits results in exclusive propagation delays. It is desirable to derive a buffer logic which has few stages so that the propagation delays are minimized. One solution to this problem in the prior art called for comparing the low voltage BIL signal with a reference voltage. Whereas the low voltage BIL signal had a wide tolerance for variations in voltage swings, the reference voltage (also known as threshold voltage or switching point reference) could not track the variations in the low voltage input.